1. Field of the Invention:
The present invention relates generally to liquid atomizing apparatus, and more particularly to a liquid atomizing apparatus which utilizes an ultrasonic wave generator having an ultrasonic vibratory member of a hollow cylindrical body.
2. Description of the Prior Art:
A prior art liquid atomizing apparatus utilizing an ultrasonic wave is shown within FIGS. 1(a) - 1(c) as comprising an ultrasonic wave transducer A, an ultrasonic horn B, an ultrasonic wave oscillator C, a liquid amount-adjusting means D, and a liquid supply pipe E. The aforenoted ultrasonic horn B has a nozzle passageway B5 disposed along the longitudinal axis thereof, and a liquid supply passageway B4 which is in communication with the nozzle passageway B5 and which is located at a position at which a node of the longitudinal vibration of the ultrasonic horn exists. Coupled to the mechanical vibration input end B1 of the ultrasonic horn B is the ultrasonic wave transducer A, and the liquid supply pipe E is connected to the liquid supply passageway B4.
An electric oscillation produced by means of the ultrasonic wave oscillator C is transformed into a mechanical vibration or a longitudinal vibration by means of the ultrasonic wave transducer A, and subsequently, the vibration thus transformed is in turn transmitted to the ultrasonic horn B whereby the amplitude of the longitudinal vibration is amplified so that the mechanical vibration output end B2 of horn B generates ultrasonic vibrations of a large amplitude. The amount of liquid being supplied is of course adjusted by means of the liquid amount-adjusting means D, and subsequently, the liquid is supplied by means of the liquid supply pipe E, liquid supply passageway B4, and nozzle passageway B5 to the mechanical vibration output end B2 of the horn B. The liquid thus supplied is spread over the vibrating surface due to the ultrasonic vibrations and is then divided into groups of minute liquid particles which division process is followed by sprinkling from the vibrating surface so as to result in the atomization desired.
With the prior art liquid atomizing apparatus utilizing ultrasonic waves, the vibrating surface for atomizing the liquid is embodied within the mechanical vibration output end of the ultrasonic horn, and consequently, the area of the vibrating surface for atomizing the liquid is primarily governed by means of the area of the aforenoted output end. Included as ultrasonic horns which may be utilized within the atomizing apparatus are a conical type shown at B within FIG. 1(a), an exponential type shown within FIG. 1(b), a step type shown within FIG. 1(c), or the like. However, the amplitude amplifying rate within such types of ultrasonic horns depends upon the ratio of the area S1 of the mechanical vibration input end B1 to the area S2 of the mechanical vibration output end B2, that is, S1/S2. Consequently, the smaller the area of the mechanical vibration output end B2, the greater will be the amplifying rate of the vibrational amplitude.
However, in order to amplify the vibrational amplitude to a degree which facilitates sufficient atomization of the liquid, it is required that the area of the mechanical vibration output end B2 be reduced to a value of approximately one tenth of the area of the input end B1. In addition, the diameter of the mechanical vibration input end B1 should not be more than one fourth of the wave length .lambda. of the ultrasonic waves in order to effectively amplify the amplitude of the ultrasonic vibrations. It follows from the foregoing that the prior art liquid atomizing apparatus suffers from the disadvantage that the amount of liquid which may be atomized per unit of time is limited to an extremely small amount due to the aforenoted limitation upon the area of the vibrating surface B2 to be used for atomization of the liquid. For example, in the instance of using an ultrasonic wave of 40 KHz, the diameter of the input end of the ultrasonic horn will be 3 cm, while the diameter of the output end will be 0.9 cm.
Still further, in the instance wherein a liquid is to be atomized by use of ultrasonic vibration and the amount of liquid being supplied is less than such an amount that liquid films, formed as a result of the ultrasonic vibration, are spread over the entire vibrating surface, then the atomizing condition is maintained stable and the distribution of the size of the atomized liquid particles remains unchanged irrespective of the amount of liquid being supplied up to such value. However, if the amount of liquid being supplied is increased to more than the aforenoted amount or value, then the thickness of the liquid films will be increased due to the restricted limitation of the vibrating surface area. Atomization of the liquid is nevertheless achieved, however, if the film thickness exceeds a given value, then the atomizing conditions will be unstable, with the resulting increase in the size of the liquid particles. Therefore, in order to achieve consistent atomization of the liquid having uniformly sized particles, even under the condition wherein the amount of liquid being supplied is increased, it is imperative that the thickness of the liquid films being created upon the vibrating surface be maintained to less than a given value.
Nevertheless, prior art liquid atomizing apparatus have very limited vibrating surface areas, whereupon the thickness of the liquid films created upon the vibrating surface will be increased to a value greater than that desired except under the condition that a very small amount of liquid is being atomized, and consequently, the apparatus fails to achieve the desired stable atomization of the liquid. In addition, with prior art liquid atomizing apparatus, the liquid is supplied directly to the positions which correspond to the crests or antinodes of the vibrational waves, and therefore, in the instance that a large amplitude of vibration is present, there results a sprinkling of extremely large-sized liquid particles.